1. Field of the Invention
The present invention relates to a method of controlling a high-current load, and, more particularly, to a method of controlling a high-current load dependent upon at least one predetermined condition.
2. Description of the Related Art
Power can be applied to a load upon the presence of a predetermined condition using a so-called "two wire" connection. In a two wire control system, a same power source supplies power to both the load and a control circuit which includes a sensor for determining the presence of the predetermined condition. Power is cyclically switched between the load and the control circuitry via a switch controlled by the control circuitry. In order to maintain operation of the sensor and other electronics while power is being diverted to the load, the control circuitry includes an electrical energy storage device which stores enough electrical energy to maintain operation of the sensor and the associated electronics while power is being diverted to the load. In order to ensure that the voltage level supplied by the storage circuit does not drop below a minimum level required for operation of the sensor and the electronics, the voltage output by the storage circuit is continuously monitored. When this storage circuit voltage falls below a predetermined level, power is diverted back to the control circuitry from the load in order to replenish the storage circuit. When the storage circuit voltage has reached a predetermined target voltage, the power source can again be connected to the load while the electrical energy stored in the storage circuit is used to operate the control circuitry.
A problem is that monitoring the voltage output from the storage circuit adds to the complexity and expense of the control circuitry. In cases where the storage circuit output voltage declines with time in a repeatable and predictable manner, the monitoring of this storage circuit output voltage represents a waste of resources. Also, if the circuitry which monitors the storage circuit output voltage is damaged or otherwise inoperable, it is possible for either the load or the control circuitry to lose power.
What is needed in the art is a method of maintaining a minimum level of electrical energy within a storage circuit while a power source is being diverted to a load, such that monitoring of the voltage output of the storage circuit is not required.